Diabetes mellitus has become an endemic disease that afflicts close to 29 million patients in the US. One of the underlying causes of diabetes is the impaired function or loss of insulin-producing beta cells that reside within the pancreas. As a consequence, patients suffering from either type 1 or type 2 diabetes have to rely on exogenous injections of insulin to regulate their blood sugar levels. Recent advances in stem cell biology are now making it likely that it will be possible to generate functional insulin-producing cells frm human stem cells, thus producing a renewable source of cells that could be used for therapeutic purposes to restore normal blood sugar levels. However, while dramatic advances have been made in the recent past, the current beta cells derived from stem cells are not fully matured and thus not fully functional. In this proposal, we describe preliminary studies indicating that programing of cellular metabolism plays an important role during the maturation of beta cells after birth. We demonstrate that mTOR signaling and its downstream components regulated by the transcription factor Hif1? regulate critical aspects of cellular metabolism during functional maturation of beta cells. The focus of this proposal is to define the roles of the mTOR and Hif1? signaling during the neonatal process of beta cell maturation in rodent and humans. We are proposing three specific aims using a combination of sophisticated transgenic mouse models and immature human beta-like cells we have generated from human embryonic stem cells. Our studies will define the role and relationships between the mTOR and Hif1? signaling cascades during rodent and human beta cell maturation. The overarching goal is to define the signals that guide this process with the intent of manipulating them to generate fully matured and functional human beta cells from stem cells. We envision that these efforts will provide novel and important information that can accelerate cell therapy approaches for the treatment of diabetic patients.